For the second year in a row, they went to investment guru Warren Buffet, with $36bn, and Microsoft co-founder Paul Allen, who is worth $22bn.

The main winners came from the technology sector - with Larry Ellison of Oracle, Michael Dell of Dell Computers, and Steve Ballmer of Microsoft all seeing their wealth increase.

Amazon.com chief Jeff Bezos' fortune jumped by $3.1bn to $5bn in line with a sharp increase in his company's share price.

Yahoo co-founder David Filo also made impressive gains, with his personal fortune rising threefold to $1.6bn.

Other winners came from the media sector, with the two daughters of the owner of cable operator Cox Communications, radio and TV owner John Kluge of Metromedia, and Sumner Redstone of Viacom all worth around $10bn each.

The five children of Sam Walton, the founder of Wal-Mart, are worth $20.5bn each - making that family collectively the richest on the list.

Californian dreams

Mr Bezos and Mr Filo both shot up the league table, occupying the 32nd and 162nd spots respectively.

The rich-list also showed that wealth is continuing to move west: California now has twice as many top tycoons as New York.

California had 95 of the 400 richest people, compared to 47 for New York.

When Forbes launched the list 21 years ago, 81 of the top 400 came from New York and just 56 from California.

"There's been an enormous shift in the geographic distribution of wealth," said Forbes senior editor Peter Newcombe.

The year's losers included Gary Winnick, who founded the now bankrupt telecoms firm Global Crossing.

Global Crossing collapsed under $12.4bn of debt; Mr Winnick's name has dropped off the Fortune 400 list.